1. Field of Invention
The present invention relates to a multimedia data transmission or broadcasting, particularly, a Video on Demand (VoD) method for transmitting multimedia data such as movie or video data according to the request of a subscriber and an apparatus thereof.
2. Description of the Related Technology
VoD technology can be classified into true VoD (TVoD) scheme, which provides one channel to a subscriber who requests video data so that each subscriber occupies a channel respectively, and near VoD (NVoD) scheme, which transmits a certain video stream periodically and can serve a plurality of subscribers by a single channel. The NVoD scheme, comparing to the TVoD scheme, can accommodate more subscribers at the same time and is very useful when broadcasting, for example, a popular video movie that many subscribers want to watch simultaneously.
A conventional NVoD system broadcasts video data via a static channel repeatedly and periodically. Specifically, the conventional NVoD system broadcasts each full video data through more than one static channel. Each static channel starts to transmit video data by a certain period.
A video data is an aggregate of large volume data such as moving picture and sound so that relatively large channel bandwidth, which costs much, is required in order to transmit the video data via network. In the NVoD scheme, the channel bandwidth is closely related to waiting time during which a subscriber waits to watch video. In particular, if the channel bandwidth, i.e., the number of channels, is increased, the waiting time can be reduced. But, the channel bandwidth is a finite and valuable resource, so it is important to increase the efficiency of channel bandwidth in order to transmit a video data stream as many as possible via the same number of channels.